This invention relates in general to pulverized fuel handling equipment and more particularly to a pulverized fuel delivery method and a system which is capable of injecting pulverized coal into a blast furnace to replace a portion of the coke normally consumed thereby.
In the smelting of iron ore in a blast furnace, coke has been traditionally the material used to provide the carbon and heat necessary for the smelting process. Coke, which normally constitutes about one-third of the furnace charge, is about the most expensive commodity in the production of iron. Consequently, replacement of a portion of the coke used with cheaper coal is of economic importance.
Various prior art systems are available for injecting pulverized coal into a blast furnace to replce part of the coke otherwise consumed, as for example the pulverized coal firing system described by U.S. Pat. No. 3,150,962 issued to L. Pearson, and that described by U.S. Pat. No. 3,301,544 issued to N. W. Eft et al.
The present invention provides a somewhat more sophisticated pulverized coal delivery system for a blast furnace which is capable of automatic operation to meet the varying coal requirements of the blast furnace. In the system of the invention, pulverized coal is delivered in dense phase fluidized form into the blast furnace from gas pressurized tanks that are placed in communication one at a time, in cyclical sequence with a pneumatic transport means. The tank gas pressure is regulated in accordance with the blast furnace wind rate to control the weight flow of pulverized coal into the furnace. The transport gas flow rate is regulated in accordance with the pulverized coal weight flow rate so as to maintain a prescribed transport gas flow rate per pound of coal delivered into the furnace.
Within the system, means are provided for sensing the rate at which pulverized coal is withdrawn from the tanks and for regulating, in accordance with the coal withdrawal rate, the output of the pulverized coal supply means that replenishes the tanks so as to maintain a predetermined total quantity of pulverized coal stored in the system. This assures that there will be an adequate reserve of pulverized coal always available for delivery to the furnace even though the coal consumption rate may fluctuate over a wide range.
The pulverized coal delivery system includes a coal pulverizer which operates to convert the coal as delivered into a dried, pulverized product, a reservoir which receives and stores the pulverized coal output of the pulverizer system and distributor means connected to the reservoir and to feed tanks associated therewith whereby the furnace is supplied from a feed tank through pneumatic transport means. This distributor means also includes multiple valved coal lines for controlling coal flow from the reservoir to the individual feed tanks to replenish them one at a time in a cyclical sequence that is in staggered relation with respect to the coal delivery sequence from the feed tanks to the furnace. Three or more feed tanks are provided so that while one tank is feeding coal to the furnace, the second tank in the sequence is in reserve, filled with coal and pressurized, and thus is instantly available for feeding the furnace as soon as the first tank approaches the empty condition, while the third tank in the sequence is being refilled from the reservoir. With this arrangement uninterrupted coal feed to the furnace is assured, since regardless of which particular tank is feeding the furnace, there will always be a pressurized full tank of pulverized fuel available in reserve.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects obtained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention .